Rob_Roy. Some B&S engines have a tendency to have the valve seat fall out of the head, which can cause what you have witnessed. Head gaskets are pretty cheap for those engines, take the head off and see what is going on. If the valve seat has fallen out, you can likely "stake" it back in place with a hammer and punch.
Kohler, Tecumseh and even Wisconsin used them on several models. I thought that was also the case for many of the larger Briggs engines in the 1980s. I seem to remember a spring loaded weight on the cam of an 11hp vertical shaft Briggs I/C mower engine that I tore apart and repaired fifteen years ago.
Stratton, Shiely and the rest of Briggs’ management missed yet another development in the marketplace. In the early 1990s there was a growing consciousness of environmental damage done by emissions from even small gasoline-powered engines, and a growing interest in the industry to respond to that by developing battery-powered lawnmowers orIn the case of Briggs & Stratton's bankruptcy, the $5 million surety bond and agreement proceeds will be used to pay unsatisfied claims by former Briggs & Stratton workers. Without these sources